Hi guys! I've got a YSL-653 I bought for cheap not too long ago and it's just lovely. The issue with it is it's missing plating on the inner slide which makes 5th position and beyond pretty much unusable. The rest of the horn is in functional condition but I want to see about replacing the slide. I can't find anything for this model so I've got a few questions. Could I use the inner slide from a YSL-354 and if not could I just use the whole slide from a 354? Maybe any other places I can look for parts etc? I want to get this horn back up to 100% as soon as I can!

Yamaha parts are pretty easily available. I suggest taking it to a tech to see if you can get replacement inners. It'll probably be less than getting a used 354 to be honest. A tech may be able to simply rotate the inners and get good results too.